The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to implement voltage regulators including linear voltage regulators. During normal operation, when the output voltage that was generated by the voltage regulator reached a desired operating value the voltage regulator disabled the output transistor. The output transistor remained disabled until such time as the output voltage decreased to a value that was below the desired operating value. An external filter capacitor and a load typically were connected to the output of the regulator. During the time that the output transistor was disabled, leakage current from the output transistor would flow through the external filter capacitor and continue to charge the filter capacitor. The leakage current charged the capacitor and the voltage on the capacitor increased in value and could reach a value that would cause damage to the load. In some cases, a resistor was connected between the output transistor and ground so that the leakage current from the transistor would flow through the resistor and not flow through the filter capacitor. One problem with such configurations was power dissipation. The leakage current flowing through the resistor increased the quiescent current consumption and, correspondingly, the power dissipation of the voltage regulator. Typically, the average quiescent current consumption of a voltage regulator using such a resistor configuration was no less than about fifty-five micro-amps.
Accordingly, it is desirable to have a method of forming a voltage regulator that reduces quiescent current consumption, and that maintains the output voltage below a value that damages the load.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor.